Heat exchange devices, such as cooling plates, are used to reduce thermal loads or to manage thermal loads for a variety of applications. For example, aircraft, spacecraft, automobiles and other land-based vehicles, and ships and other water-based vehicles may use heat exchange devices to manage thermal loads. The thermal loads may be caused by onboard equipment, the environment, other sources, or a combination of sources. To illustrate, aircraft may use cooling plates to manage heat loads associated with avionics and printed circuit boards, aircraft engines, and so forth. Additionally, aircraft may use cooling plates for thermal protection systems to preserve underlying air frame structure from exposure to disruptive heat fluxes generated due to fluid resistance (e.g., air friction) or by portions of the air frame being subjected to high temperature exhaust. In another illustrative example, tanks or other land-based vehicles may use heat exchange devices to manage thermal loads from environmental exposure, engines, or other heat sources.
Managing thermal loads can be expensive in terms of equipment cost, operational costs, weight, space constraints, and so forth. Equipment cost, operational cost, weight, and space constraints are generally of concern whether a heat exchange device is intended for use in an aircraft, a land-based craft, a water-based craft, a spacecraft or even a fixed structure, such as a building. For example, certain heat exchange devices may be associated with relatively high equipment costs. For example, heat exchange devices that use brazed aluminum foam and metal fins may have high manufacturing costs due to manufacturing difficulties (such as high temperature soldering) associated with these devices. Accordingly, the equipment costs of such devices may be relatively high.
In an example illustrating operational costs, heat exchange devices can be an operational penalty when used in a vehicle due to increased weight of the vehicle to provide for plenums to route coolant and other equipment associated with the heat exchange devices, such as equipment used to pressurize the coolant. The vehicle may also incur other operational penalties. To illustrate, certain aircraft may use ram air as a coolant. When ram air is used as the coolant, the ram air may be diverted from the aircraft's engines. Diverting air from an aircraft engine for use as ram air coolant can reduce operational efficiency of the aircraft engine resulting in higher operational costs and/or less than optimal performance. Generally, the more air that is diverted, the greater the operational cost that is added to the aircraft. Other vehicles may also incur operational costs due to heat exchange devices.
Particular vehicles may use heat exchange devices for thermal protection systems to provide structural cooling of the vehicle. Examples of thermal protection systems include back side cooling systems, film cooling systems and transpiration cooling systems. Back side cooling systems blow coolant through a duct on the back side of the structure to be cooled, away from a side experiencing heat flux. Film cooling systems blow coolant from a plenum on the back side of the structure through closely spaced holes in the structure itself. The coolant may form a film on the side of the structure being heated that protects the structure and controls the interface temperature. Transpiration cooling systems intimately cool a porous structure by flowing cooling air directly through the porous structure from a back side plenum.
Back side cooling systems, film cooling systems and transpiration cooling systems may use relatively high coolant flow rates to achieve the desired cooling. Further, each of these systems may use heavy, expensive structural ducting and plenum systems to deliver coolant to an area to be cooled. For example, a plenum may be provided directly behind each area needing cooling. Further, film cooling systems may be expensive due to the cost of providing a large number of small holes in the surface to be cooled. Transpiration systems may be limited by ceramic and sintered metal porous materials used for the surface to be cooled.